Tracking bird flu: US wildlife workers on the front line against deadly strains

This bar-headed goose (Anser indicus) was marked with a satellite transmitter at Qinghai Lake, China, in an effort to understand the role that wild birds play in avian influenza.

They were once featured on the show “Dirty Jobs” but the wildlife experts who spend weeks each year wrestling wild birds to swab their behinds for avian flu don’t mind. They’re happy to be on the front line, keeping an eye out for infected birds that might bring new and deadly strains of influenza to the United States.

The program’s been dialed back a bit since it started in 2005, but the U.S. Geological Survey and Fish and Wildlife Service experts are paying close attention to reports of a new and deadly strain of bird flu – the H7N9 virus. It’s infected 102 people in China at last count, and killed 20 of them.

No one is sure where, exactly, it’s coming from. Domestic chickens don’t seem to be a source, nor do pigs, and the virus has been traced to pigeons and finches. It doesn’t seem to be spreading from person to person easily.

“Right now the situation in China seems to be more of a public health situation than a wildlife situation,” says Hon Ip, who has been working on the avian surveillance program since it started up in 2005.

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An H7N9 bird flu patient is escorted after his recovery and approval for discharge from the hospital in Bozhou, central China's Anhui province .

“We are going to see whether it really is going to be extensively in wildlife before we ramp up our surveillance in this country.”

The bird surveillance program started as concern grew over H5N1 – the other bird flu virus – which has spread to 15 countries since 2003, infecting more than 600 people and killing about 60 percent of them.

Ip and his colleagues showed the H5N1 virus was definitely spread by migrating birds, but they’ve also shown, so far, that the highly pathogenic type has not yet come to the U.S.

Just about every other type of bird flu has, however. Birds can carry dozens of different varieties of influenza, and some make them sick, while others don’t. There’s highly pathogenic influenza – high-path for short – that can sweep through a flock of chickens in days. Other types don’t seem to cause so much as a sniffle in birds.

And different species are infected differently. Dometic ducks don’t seem to be bothered by H5N1, but they can give it to chickens which, in turn, can sometimes infect people.

The best way to check is to test the birds. This is where “Dirty Jobs” comes in. People are tested for flu with a nasal swab. You can test birds this way, too, but they also spread flu in their feces. So they need a swab of the cloaca – the all-purpose opening that birds have on the back end.

“Yes, it’s a dirty job,” Ip says, laughing. The Discovery Channel show featured the USGS and Fish and Wildlife Service project during season 3 in 2007.

The team has tested more than 450,000 migratory birds from 284 different species in all 50 states. Now they focus on Alaska, Maine and Iceland. The USGS National Wildlife Health Center also tests sick and dead migratory birds, especially ducks, geese and swans.

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A staff member wears a protection suit while spraying disinfectant to the hen house whose proprietor tested positive for H7N9 virus in Tianchang, China

“We are working a lot smarter. We kind of know which locations are better,” Ip says. Waterfowl were especially likely to carry H5N1. But H7N9 looks different.

Genetic tests suggested one ancestral carrier was a finch, and other tests suggested pigeons might carry it. “Should it ever be in wild birds, there is a possibility it may be in species other than waterfowl. We need to know that,” Ip says.

The finch species is found across the northern hemisphere, in Asia, Europe and North American. “It is called a brambling,” Ip says. “There are some bramblings that come straight into Alaska and into the lower 48. These little birds are just amazing. They are so small and yet able to migrate these incredible distances.”

The little orange and gray birds have not been shown yet to carry H7N9. Instead, genetic tests showed they may have carried some of the genes that mixed with genes from other bird flu viruses to create H7N9. Flu viruses do this kind of thing all the time – an animal can be infected with more than one type of flu strain at once, and the viruses meet up and swap genetic material.

That is what happened with the 2009 pandemic of H1N1 swine flu. The new virus was an indirect descendant of the 1918 “Spanish Flu” that killed upwards of 50 million people. Over the decades, it picked up genes from various types of bird and pig influenzas.

“It was a virus that ultimately came from birds but it evolved in swine before it became a human pandemic virus,” Ip says. “Maybe new mammalian viruses can arise when mammals are directly infected by birds.”

So far, neither H5N1 nor H7N9 seems to have developed the ability to pass easily from one person to another. If one or the other does, however, experts worry. “Whenever a new type of influenza virus infects humans it is a cause for concern,” says Jim Pipas, a virologist at the University of Pittsburgh. “First, because H7N9 is so different from influenza viruses currently circulating in the human population, humans are likely to lack an effective immune response to the virus. … This is why it is so important to maintain surveillance and to be ready to produce a vaccine if necessary.”